Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$47.94	11.671%	$53.5351	$53.54	$53.55	$53.50
Purchase #2	$245.26	4.543%	$256.4022	$256.40	$256.40	$256.40
Purchase #3	$149.68	4.840%	$156.9245	$156.92	$156.90	$156.90
Purchase #4	$246.75	9.166%	$269.3671	$269.37	$269.35	$269.40
Purchase #5	$6.53	7.391%	$7.0126	$7.01	$7.00	$7.00
Purchase #6	$196.70	13.285%	$222.8316	$222.83	$222.85	$222.80
Purchase #7	$83.41	3.372%	$86.2226	$86.22	$86.20	$86.20
7 purchase totals =	$976.27		$1,052.2957	$1,052.29	$1,052.25	$1,052.20